1. Field of the Invention
The present invention relates to a lean NOx trap type exhaust gas purifying catalyst and an exhaust gas cleaning system.
More specifically, the present invention relates to a lean NOx trap type exhaust gas purifying catalyst with excellent durability, and an exhaust gas cleaning system equipped with this exhaust gas purifying catalyst.
2. Background Information
In the prior art, there have been proposed an exhaust gas purifying catalyst that adsorbs NOx to a NOx adsorbent in a lean atmosphere, and releases the NOx from the stoichiometric mixture or a rich atmosphere for reductive cleaning. More specifically, the exhaust gas purifying catalyst is a mixture of a first powder prepared by carrying platinum on a first carrier made of porous grains and a second powder prepared by carrying rhodium on a second carrier. Here, the NOx adsorbent is carried on the first carrier described above, and the second carrier described above is made of zirconia stabilized by alkaline earth metal or rare earth element (excluding cerium) (see Japanese Patent No. 3741303).